Ball valves are often subjected to extremely high pressures and temperatures in the various processes where they are used. Leaking past seals associated with the rotatable closure members present operational issues. The tendency for valves to leak increases under conditions of high pressure and high temperature, which is known to occur in service valves which operate through a wide range of temperatures. Further, such valves may rely on a high pressure differential to effect a tight seal in the reverse direction, i.e., when a higher pressure is applied to the normally low pressure or outlet side of the valve, and may have a tendency to leak excessively at lower pressures insufficient to fully engage the high pressure seal.